Lennox ML196DF045XE36B User manual

Page 1 ©2021 Lennox Industries Inc.
Litho U.S.A.
Corp. 1910-L7
02/2021 ML196DFE
Service Literature
ML196DFE SERIES UNITS
ML196DFE series units are high-efficiency gas fur
naces manufactured with Lennox DuralokPlustalumi
nized steel clamshell-type heat exchangers, with a stainless
steel condensing coil. ML196DFE units are available in
heating input capacities of 44,000 to 110,000 Btuh and
cooling applications from 2 through 5 tons. Refer to Product
Specifications for proper sizing.
Units are factory equipped for use with natural gas. A kit is
available for conversion to LP/Propane operation. All
ML196DFE units are equipped with a hot surface ignition
system. The gas valve is redundant to assure safety
shut-off as required by C.S.A.
The heat exchanger, burners and manifold assembly can be
removed for inspection and service. The maintenance section
gives a detailed description on how this is done.
All specifications are subject to change. Procedures outlined
in this manual are presented as a recommendation only
and do not supersede or replace local or state codes.
WARNING
Electric shock hazard. Can cause injury
or death. Before attempting to perform
any service or maintenance, turn the
electrical power to unit OFF at discon
nect switch(es). Unit may have multiple
power supplies.
Table of Contents
Specifications 2.................................
Optional Accessories 3..........................
Blower Performance Data 4......................
I-Unit Components 5............................
II Placement and Installation 19....................
III-Start-Up 39...................................
IV-Heating System Service Checks 40..............
V-Typical Operating Conditions 44.................
VI-Maintenance 45...............................
VII-Wiring and Sequence of Operation 48...........
VIII-Troubleshooting 49...........................
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person
al injury or loss of life. Installation and service must
be performed by a licensed professional HVAC in
staller (or equivalent), service agency or the gas sup
plier.
CAUTION
As with any mechanical equipment, contact with
sharp sheet metal edges can result in personal in
jury. Take care while handling this equipment and
wear gloves and protective clothing.

Page 2
SPECIFICATIONS
Gas
Heating
Performance
Model No. ML196DF045XE36B ML196DF070XE48B ML196DF090XE48C ML196DF110XE60C
1AFUE 96% 96% 96% 96%
Input - Btuh 44,000 66,000 88,000 110,000
Output - Btuh 42,000 64,000 85,000 106,000
Temperature rise range - °F 30 - 60 35 - 65 50 - 80 40 - 70
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane 3.5 / 10 3.5 / 10 3.5 / 10 3.5 / 10
High static - in. w.g. 0.5 0.5 0.5 0.5
Connections
in.
Intake / Exhaust Pipe (PVC) 2 / 2 2 / 2 2 / 2 2 / 2
Gas pipe size IPS 1/2 1/2 1/2 1/2
Condensate Drain Trap (PVC pipe) - i.d. 3/4 3/4 3/4 3/4
with furnished 90° street elbow 3/4 slip x 3/4 Mipt 3/4 slip x 3/4 Mipt 3/4 slip x 3/4 Mipt 3/4 slip x 3/4 Mipt
with eld supplied (PVC coupling) - o.d. 3/4 slip x 3/4 MPT 3/4 slip x 3/4 MPT 3/4 slip x 3/4 MPT 3/4 slip x 3/4 MPT
Indoor
Blower
Wheel nom. diameter x width - in. 10 x 8 11-1/2 x 10 10 x 10 11 x 11
Motor Type DC Brushless DC Brushless DC Brushless DC Brushless
Motor output - hp 1/2 3/4 3/4 1
Tons of add-on cooling 1.5 - 3 2 - 4 2 - 4 3 - 5
Air Volume Range - cfm 505 - 1455 525 - 1720 860 - 1760 1010 - 3115
Electrical
Data
Voltage 120 volts - 60 hertz - 1 phase
Blower motor full load amps 6.8 8.4 8.4 10.9
Maximum overcurrent protection 15 15 15 15
Shipping Data lbs. - 1 package 126 139 154 XXX
NOTE - Filters and provisions for mounting are not furnished and must be eld provided.
1 Annual Fuel Utilization E󰀩ciency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.

Page 3
OPTIONAL ACCESSORIES
“B” Width Models “C” Width Models
CABINET ACCESSORIES
Downow Combustible Flooring Base 11M60 11M61
CONDENSATE DRAIN KITS
Condensate Drain Heat Cable 6 ft. 26K68 26K68
24 ft. 26K69 26K69
Crawl Space Vent Drain Kit US 51W18 51W18
Canada 15Z70 15Z70
CONTROLS
Blower Relay Kit (for two-stage outdoor units) 85W66 85W66
iComfort®M30 Smart Wi-Fi Thermostat 15Z69 15Z69
Remote Outdoor Temperature Sensor X2658 X2658
Twinning Kit 16W72 16W72
DOWNFLOW FILTER KITS
1 Downow Filter Cabinet 51W07 51W08
No. and Size of lter - in. (2) 16 x 20 x 1 (2) 16 x 20 x 1
NIGHT SERVICE KIT
Night Service Kit 84W48 84W48

Page 4
ML196DF070XE48B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-High Medium Medium-Low Low
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1720 510 1545 355 1340 235 1240 190 1020 95
0.10 1700 530 1505 360 1310 245 1195 200 955 110
0.20 1675 545 1465 370 1275 255 1155 205 895 115
0.30 1640 555 1420 380 1230 270 1120 215 835 125
0.40 1600 565 1380 395 1180 280 1060 225 785 135
0.50 1560 570 1340 400 1140 290 1015 235 715 145
0.60 1500 565 1300 420 1095 305 965 245 640 150
0.70 N/A N/A 1255 430 1040 315 910 255 585 160
0.80 N/A N/A 1215 445 990 320 865 265 525 170
ML196DF045XE36B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-High Medium Medium-Low Low
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1455 370 1275 255 1175 190 920 90 865 85
0.10 1425 375 1250 260 1145 200 885 100 830 90
0.20 1395 380 1225 265 1115 210 850 110 795 95
0.30 1365 385 1195 275 1085 220 815 115 750 105
0.40 1325 385 1170 290 1045 230 770 130 700 110
0.50 1245 370 1130 300 1010 240 720 135 660 120
0.60 1180 360 1095 305 970 245 675 140 605 125
0.70 N/A N/A 1045 310 935 255 615 150 560 130
0.80 N/A N/A 1000 290 895 260 580 155 505 135
BLOWER DATA
ML196DF090XE48C PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-High Medium Medium-Low Low
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1760 435 1555 280 1405 230 1315 175 1190 135
0.10 1730 445 1515 300 1375 240 1280 190 1150 145
0.20 1700 455 1475 315 1350 250 1245 205 1115 155
0.30 1670 465 1445 330 1310 265 1200 220 1070 165
0.40 1640 480 1410 340 1265 275 1160 230 1025 175
0.50 1590 485 1380 345 1225 285 1125 235 985 185
0.60 1530 465 1340 360 1195 295 1085 245 945 195
0.70 N/A N/A 1315 370 1150 305 1065 255 895 200
0.80 N/A N/A 1280 375 1115 315 1015 265 860 210
ML196DF110XE60C PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-High Medium Medium-Low Low
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 3115 669 1895 466 1710 356 1605 285 1415 209
0.10 2090 686 1845 476 1670 368 1570 299 1380 217
0.20 2060 701 1790 487 1630 375 1520 315 1320 222
0.30 2020 711 1760 498 1590 393 1470 324 1280 236
0.40 1980 734 1715 511 1545 403 1420 342 1220 247
0.50 1935 740 1690 525 1500 418 1370 347 1170 264
0.60 1895 749 1625 536 1460 423 1335 358 1110 269
0.70 1830 738 1600 548 1410 438 1280 367 1080 286
0.80 1765 723 1550 564 1370 456 1240 387 1010 290

Page 5
FIGURE 1
CONTROL BOX
(Includes integrated control,
transformer, circuit breaker and door switch)
BAG ASSEMBLY
(shipping location)
BLOWER MOTOR
(hidden)
BURNER
ACCESS
PANEL
COMBUSTION
AIR INDUCER
BURNER BOX ASSEMBLY
(includes sensor, rollout switches and ignitor) GAS VALVE
BLOWER DECK
COLD END HEADER BOX
PRIMARY LIMIT
DuralokPlusTM
HEAT EXCHANGER
ASSEMBLY
COMBUSTION AIR INDUCER
PRESSURE SWITCH
PARTS ARRANGEMENT
BLOWER
ACCESS
PANEL

Page 6
I-UNIT COMPONENTS
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
Electrostatic discharge can affect elec
tronic components. Take precautions
to neutralize electrostatic charge by
touching your hand and tools to metal
prior to handling the control.
ML196DFE unit components are shown in figure 1. The
combustion air inducer, gas valve and burners can be ac
cessed by removing the outer access panel. The blower
and control box can be accessed by removing the blow
er access panel.
A-Control Box Components (Figure 2)
Unit transformer (T1) and integrated ignition control (A92)
are located in the control box. In addition, a door interlock
switch (S51) is located in the control box.
FIGURE 2
DOOR INTERLOCK
SWITCH (S51)
INTEGRATED IGNITION
CONTROL
(A92)
TRANSFORMER
(T1)
ML196DFE Control
Box
CIRCUIT
BREAKER
(CB8)
1. Transformer (T1)
A transformer located in the control box provides power to
the low voltage section of the unit. The transformers on all
models are rated at 40VA with a 120V primary and 24V
secondary.
2. Door Interlock Switch (S51)
A door interlock switch rated 14A at 120VAC is located on
the control box. The switch is wired in series with line volt
age. When the blower door is removed the unit will shut
down.
3. Circuit Breaker (CB8)
A 24V circuit breaker is also located in the control box. The
switch provides overcurrent protection to the transformer
(T1). The breaker is rated at 3A at 32V. If the current ex
ceeds this limit the breaker will trip and all unit operation will
shutdown. The breaker can be manually reset by pressing
the button on the face.
4. Integrated Ignition Control (A92)
WARNING
Shock hazard.
Disconnect power before servicing. Control is not
field repairable. If control is inoperable, simply re
place entire control.
Can cause injury or death. Unsafe operation will
result if repair is attempted.
The hot surface ignition control system consisting of an in
tegrated control (figure 3 with control terminal designa
tions in tables 1, 2 and 3), sensor and ignitor (figure 5). The
integrated control and ignitor work in combination to en
sure furnace ignition and ignitor durability. The integrated
control, controls all major furnace operations. The inte
grated control also features a RED LED for troubleshoot
ing and two accessory terminals rated at (1) one amp. See
table 4 for troubleshooting diagnostic codes. The nitride
ignitor is made from a non-porous, high strength propri
etary ceramic material that provides long life and trouble
free maintenance.
TABLE 1
4-Pin Terminal Designation
PIN # FUNCTION
1Combustion Air Inducer Line
2Ignitor Line
3Combustion Air Inducer Neutral
4Ignitor Neutral
TABLE 2
12-Pin Terminal Designations
PIN # FUNCTION
1High Limit Output
2Not Used
324V Line
4Not Used
5Rollout Switch Out
624V Neutral
7High Limit Input
8 Ground
9Gas Valve Common
10 Pressure Switch In
11 Rollout Switch In
12 Gas Valve Out

Page 7
TABLE 3
1/4” QUICK CONNECT TERMINALS
120HUM Humidifier 120VAC
LINE 120VAC
XFMR Transformer 120VAC
CIRC Indoor blower 120VAC
EAC Indoor air quality accessory 120VAC
NEUTRALS Common 120VAC
HUM24 Humidifier 24VAC
3/16” QUICK CONNECT TERMINALS
COOL Cooling tap 24VAC
HEAT Heating tap 24VAC
FAN Continuous blower 24 VAC
PARK (no power) Park terminal for unused speed taps
FS Flame sense
24 COM Common 24VAC
TABLE 4
The integrated control is equipped with an LED light for troubleshooting. The diagnostic codes are listed below in table 4.
RED LED
Flash Code 2Diagnostic Codes / Status of Furnace
Off No power to control or board fault detected
Heartbeat
1
Normal Operation - Idle, Continuous Fan, Cool
Continuous Rapid
Flash Call For Heat / Burner Operation
1Reverse Line Voltage Polarity
2Improper Earth Ground
3Burner failed to light, or lost flame during heat demand
4Low Flame Signal - check flame sensor
5Watchguard - burner failed to light, exceeded maximum number of retries or recycles.
6Not Used
7Primary or Secondary Limit Open or Watchguard Mode - Limit Switch Open longer than 3 min
utes
8Rollout Switch Open
9Pressure Switch failed to close or opened during heat demand
10 Watchguard - Pressure Switch opened 5 times during one heat demand
11 Pressure Switch stuck closed prior to activation of combustion air inducer
12 Flame Sensed without gas valve energized
13 Low Line Voltage
Notes
Note 1 A ”Heartbeat” is indicated by a ”Slow Flash” - 1 sec on 1 sec off, repeating
Note 2 Error codes are indicated by a ”Rapid Flash” - the LED flashes X times at 1/2 sec on 1/2 sec
off, remains off for 3 sec, then repeats
Note 3
Last 10 error codes are stored in memory including when power is shut off to the unit. - To recall,
press and release button, most recent will be displayed first, LED off for 3 sec, then next error
code is displayed, etc. To clear error codes, depress and hold button longer than 5 seconds.

Page 8
FIGURE 3
INTEGRATED CONTROL
(Automatic Hot Surface Ignition System)
BLOWER OFF DELAY
RED LED RECALL BUTTON
Electronic Ignition
On a call for heat the integrated control monitors the com
bustion air inducer pressure switch. The control board will
not begin the heating cycle if the pressure switch is closed
(by-passed). Once the pressure switch is determined to be
open, the combustion air inducer is energized. When the
differential in the pressure switch is great enough, the pres
sure switch closes and a 15-second pre-purge begins. If
the pressure switch is not proven within 2-1/2 minutes, the
integrated control goes into Watchguard-Pressure Switch
mode for a 5-minute re-set period.
After the 15-second pre-purge period, the ignitor warms up
for 20 seconds during which the gas valve opens at 19 sec
onds for a 4-second trial for ignition. The ignitor remains
energized for the first 3 seconds during the 4 second trial. If
ignition is not proved during the 4-second period, the inte
grated control will try four more times with an inter purge
and warm-up time between trials of 35 seconds.
After a total of five trials for ignition (including the initial
trial), the integrated control goes into Watchguard-Flame
Failure mode. After a 60-minute reset period, the inte
grated control will begin the ignition sequence again.
Fan Time Control
Heating Fan On Time
The fan on time of 30 seconds is not adjustable.
Heating Fan Off Time
Fan off time (time that the blower operates after the heat
demand has been satisfied) can be adjusted by moving the
jumper to a different setting. The unit is shipped with a fac
tory fan off setting of 90 seconds. For customized comfort,
monitor the supply air temperature once the heat demand
is satisfied. Note the supply air temperature at the instant
the blower is de-energized.
Adjust the fan-off delay to achieve a supply air temperature
between 90° - 110° at the instant the blower is de-ener
gized. (Longer delay times allow for lower air temperature,
shorter delay times allow for higher air temperature). See
figure 4.
Cooling Fan On Time
The fan on time is 2 seconds and is not adjustable.
Cooling Fan Off Time
The control has a 45 second fan off delay after cooling de
mand has been met. This delay is factory set and not ad
justable.
HEAT FAN‐OFF TIME IN SECONDS
To adjust fan-off timing, reposition jumper across pins to
achieve desired setting.
NO JUMPER
FIGURE 4
60 90
120
180
60 90
120
180
60 90
120
180
60 90
120
180
60 Second
off Time
90 Second
off Time
120 Second
off Time
180 Second
off Time

Page 9
FIGURE 5
ML196DFE Burner Box Assembly
SENSOR
ROLLOUT SWITCHES
GAS VALVE
IGNITOR
BURNERS
FRONT BURNER BOX PLATE
B-Heating Components
Combustion air inducer (B6), primary limit control (S10),
SureLight ignitor, burners, flame rollout switch (S47), gas
valve (GV1), combustion air prove switch (S18), and clam
shell heat exchangers are located in the heating compart
ment. The heating compartment can be accessed by re
moving the outer access panel.
1. Flame Rollout Switches (Figure 5)
Flame rollout switches S47 are SPST N.C. high temperature
limits located on the top left and bottom right of the front buner
box plate. S47 is wired to the burner ignition control A92.
When either of the switches sense flame rollout (indicat
ing a blockage in the combustion passages), the flame
rollout switch trips, and the ignition control immediately
closes the gas valve. Switch S47 in all ML196DFE units is
factory preset to open at 210_F + 12_F (99_C + 6.7_C) on a
temperature rise. All flame rollout switches are manual reset.
See table 4 flash code 8 for troubleshooting.
2. Heat Exchanger (Figure 6)
ML196DFE units use an aluminized steel primary and
stainless steel secondary heat exchanger assembly.
Heat is transferred to the air stream from all surfaces of
the heat exchanger. The shape of the heat exchanger en
sures maximum efficiency.
The combustion air inducer pulls fresh air through the burn
er box. This air is mixed with gas in the burners. The gas /
air mixture is then burned at the entrance of each clam
shell. Combustion gases are then pulled through the primary
and secondary heat exchangers and exhausted out the ex
haust vent pipe.
3. Primary Limit Control (Figure 6)
Primary limit (S10) used on ML196DFE units is located in the
heating vestibule panel. When excess heat is sensed in the
heat exchanger, the limit will open. Once the limit opens, the
furnace control energizes the supply air blower and de-en
ergizes the gas valve. The limit automatically resets when
unit temperature returns to normal. The switch is factory
set and cannot be adjusted. For limit replacement remove
wires from limit terminals and rotate limit switch 90 de
grees. Slowly remove from the vestibule panel. Install re
placement limit with same care.

Page 10
FIGURE 6
Primary Limit Location and Heat Exchanger
Install limit face down
4. Gas Valve (GV1)
The ML196DFE uses an internally redundant to valve to as
sure safety shut‐off. If the gas valve must be replaced, the
same type valve must be used.
24VAC terminals and gas control switch are located on
top of the valve. All terminals on the gas valve are con
nected to wires from the ignition control. 24V applied to the
terminals opens the valve.
Inlet and outlet pressure taps are located on the valve. A
manifold adjustment screw is also located on the valve. An
LP/Propane changeover kit is available.
FIGURE 7
GAS VALVE SHOWN IN ON POSITION
MANIFOLD
PRESSURE
OUTLET
PORT
INLET
PRESSURE
PORT
MANIFOLD PRESSURE
ADJUSTMENT SCREW
(under barbed fitting)
5. Flame Sensor (Figure 5)
A flame sensor is located on the left side of the burner sup
port. The sensor is mounted on the bottom burner box plate
and the tip protrudes into the flame envelope of the left-
most burner. The sensor can be removed for service with
out removing any part of the burners. During operation,
flame is sensed by current passed through the flame and
sensing electrode. The ignition control allows the gas valve
to remain open as long as flame signal is sensed.
NOTE - The ML196DFE is polarity sensitive. Make sure
that the furnace is wired correctly and is properly grounded.
A microamp DC meter is needed to check the flame signal
on the integrated control.
Flame (microamp) signal is an electrical current which passes
from the integrated control to the sensor during unit operation.
Current passes from the sensor through the flame to ground to
complete a safety circuit.
To Measure Flame Signal - Integrated Control:
Use a digital readout meter capable of reading DC micro
amps. See figure 8 for flame signal check.
1 - Set the meter to the DC amps scale.
2 - Turn off supply voltage to control.
3 - Remove sensor wire from integrated control.
4 - Connect (-) lead to flame sensor wire.
5 - Connect (+) lead to Terminal FS on integrated control.
6 - Turn supply voltage on and close thermostat contacts to
cycle system.
7 - When main burners are in operation for two minutes, take
reading.
6. Ignitor (Figure 5)
ML196DFE units use a mini-nitride ignitor made from a pro
prietary ceramic material. To check ignitor, measure its re
sistance and voltage. A value of 39 to 70 ohms indicates a
good ignitor. Voltage to the ignitor should be 102VAC -
132VAC. See figure 9 for resistance and voltage checks.

Page 11
FIGURE 8
Measuring Flame Signal
Flame Signal In Microamps
Normal Low Drop Out
1.5 0.5 - 1.4 0.4
(+)
Set Dial to DC MicroAmps
(+)
Multi−Meter
(+) To Control
Sensor T erminal
(−) To Flame
Terminal
Remove Sensor Wire from
Intergrated Control and
Connect Alligator Clip (+)
to Terminal on Control
Flame Sensor
Terminal
Flame Sensor
Wire
Remove Sensor Wire from
Intergrated Control and
Connect Alligator Clip (−)
to Frame Sensor Lead
Intergrated
Control

Page 12
FIGURE 9
Test 2
Check ignitor for correct resistance.
Seperate the 2-pin jack-plug near the manifold
and check resistance of ignitor at the plug.
Reading should be between 39 and 70 ohms. If
the reading is correct, then the problem is with
the wiring between the jack-plug and the control.
If reading is not correct, the issue is the ignitor.
Integrated Control Detail
Integrated Control Detail
Test 3
Check ignitor for correct voltage
Insert meter probes into terminals 2 and 4 (use small
diameter probes in order not to damage plug).
Check voltage during 20 second ignitor warm up period.
Voltage should read 120 volts + 10%. If voltage reads below
these values, check for correct supply voltage to furnace.
Integrated Control Detail
Test 1
Check ignitor circuit for correct resistance.
Remove 4-pin plug from control.
Check ohms reading across terminals 2 and 4.
Reading should be between 39 and 70 ohms. If
value is correct, this is the only test needed.
If the reading on the meter is not correct, (0 or
infinity) then a second test is needed.

Page 13
7. Combustion Air Inducer (B6)
& Cold End Header Box
All ML196DFE units use a combustion air inducer to
move air through the burners and heat exchanger during
heating operation. The blower uses a shaded pole
120VAC motor. The motor operates during all heating op
eration and is controlled by burner ignition control A92.
Blower operates continuously while there is a call for heat.
The burner ignition control will not proceed with the ignition
sequence until combustion air inducer operation is sensed
by the proving switches.
The CAI is installed on the cold end header box. The cold
end header box is a single piece made of hard plastic.
The box has an internal channel where the combustion
air inducer creates negative pressure at unit start up. The
channel contains an orifice used to regulate flow created
by the CAI. The box has pressure taps for the CAI pres
sure switch hoses. The pressure switch measure the
pressure across the CAI orifice or difference in the chan
nel and the box. If replacement is necessary the gas
kets used to seal the box to the vestibule panel and
the CAI to the box, must also be replaced.
TABLE 5
ML196DFE Unit C.A.I. Orifice Size
-045 0.618”
-070 0.810”
-090 0.905”
-110 1.100”
8. Combustion Air Pressure Switch
(Figure 10)
ML196DFE series units are equipped with a differential
pressure switch located on the cold end header box. The
switches monitor across the CAI orifice to insure proper flow
through the heat exchanger.
The switch is a SPST N.O. prove switch electrically con
nected to the integrated control. The purpose of the switch is
to prevent burner operation if the combustion air inducer is not
moving enough air for proper combustion.
FIGURE 10
Pressure Switch
24VAC
TERMINALS
BRACKET
TAP
TAP
On start‐up, the switch senses that the combustion air inducer
is operating. It closes a circuit to the ignition control when
the difference in pressure across the CAI orifice exceeds a
non-adjustable factory setting. If the switch does not suc
cessfully sense the required differential, the switch can
not close and the furnace cannot operate. If the flue or
air inlet become obstructed during operation, the switch
senses a loss of pressure differential and opens the circuit to
the ignition control. If the condensate line is blocked, water
will back up into the header box and reduce the pressure dif
ferential across the switch. The prove switch opens if the dif
ferential drops below the set point. See table 6.
Checks of pressure differential can aid in troubleshooting.
When measuring the pressure differential, readings should be
taken at the pressure switch. See figure 11 and table 7. Lack
of differential usually indicates problems in the intake or ex
haust piping, but may indicate problems in the heat ex
changer, condensing coil, header boxes, combustion
inducer or other components.
TABLE 6
ML196DFE
Unit
Altitude ft
0 - 4500 4501 - 7500 7501 - 10000
Set Point SetPoint Set Point
-045 -0.65 -0.60 -0.55
-070 -0.90 -0.80 -0.70
-090 -0.90 -0.85 -0.65
-110 -1.00 -0.85 -0.65
*Set point is factory set and non-adjustable

Page 14
FIGURE 11
Measuring Pressure Differential
1 - Remove thermostat demand and allow unit to
cycle off.
2 - Install a tee in the negative (-) line (red and black tubing
or red tubing) and a tee in the positive (+) line (black
tubing) running from the pressure switch to the cold
end header box.
3 - Install a manometer with hose from the negative (-)
side of the manometer to the tee installed in the
negative (-) line and with hose from the positive (+)
side of the manometer to the tee in the positive (+)
line.
NOTE - Both sides of the cold end header box are
negative. However the (+) port reads less negative pres
sure than the (-) port.
4 - Operate unit and observe manometer reading.
Readings will change as heat exchanger warms.
a. Take one reading immediately after start‐up.
b. Take a second reading after unit has reached
steady state (approximately 5 minutes). This will be
the pressure differential.
The pressure differential should be greater
than those listed in table 6.
5 - Remove thermostat demand and allow to cycle off.
6 - Remove manometer and tee's. Reinstall combustion
air sensing hoses to the pressure switch.
To Cold End Header Box
Field Provided Tubing
To Pressure Switch
To Cold End Header Box
Black Tubing
(positive +)
Red and Black Tubing
or Red Tubing
(negative -)
“+”
High
“-”
Low

Page 15
TABLE 7
Problem Corrective Action
Pressure switch stuck closed Check that the pressure switch is open without the combustion air inducer operat
ing. Replace if defective.
Pressure switch does not close due to
obstruction in vent pipe.
Check for restricted vent. Remove all blockage.
Check for proper vent sizing. See table 12.
Pressure switch does not close due to
incorrect routing of the pressure
switch tubing.
Check that the pressure switch tubing is correctly routed. Correctly route pressure
witch line.
Pressure switch does not close due to
obstructions in the pressure switch
line.
Remove any obstructions from the the pressure switch line and/or taps
Pressure switch tubing damaged. Check pressure switch tubing for leaks. Replace damaged tubing if necessary.
Condensate in pressure switch tubing. Check pressure switch tubing for condensate. Remove condensate from tubing.
Pressure switch does not close due to
a low differential pressure across the
pressure switch.
Check the differential pressure across the pressure switch.
Check for restricted inlet vent. Remove all blockage.
Check for proper vent sizing and run length. See table 12.
Wrong pressure switch installed in the
unit, or pressure switch is out of cal
ibration
Check that the correct pressure switch is installed in the unit. Replace pressure
switch if necessary.
Miswiring of furnace or improper con
nections at pressure switch.
Check for correct wiring and loose connections. Correct wiring and/or replace any
loose connections.
Pressure switch failure. If all the above modes of failure have been checked, the pressure switch may have
failed. Replace pressure switch and determine if unit will operate.
Damaged condensate trap. Check trap for any cracks or damage and replace if necessary.
Cold end header box does not drain
properly.
Check that the furnace is set properly with a slight tilt (0 - 1/2”) towards the front
if necessary. See furnace installation instruction.
Air leakage around the combustion air
inducer gasket. Check gasket and replace if necessary.
Air leakage around the cold end head
er box gasket. Check gasket and replace if necessary.
Damaged cold end header box tubing. Check tubing and replace if necessary.
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
É
É
DEMAND
CAI
GAS VALVE
15
ON
OFF
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
É
É
38
ÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉ
IGNITOR
341
Pre -Purge Ignitor Warm-up Trial for
Ignition Post
Purge
5 SEC80
*Blower on time will be 30 seconds after flame is sensed. Blower off time will depend on “OFF TIME” Setting.
INDOOR BLOWER
ÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉ
Blower “On”*
Delay
ELECTRONIC IGNITION
FIGURE 12

Page 16
C- Blower Compartment
IMPORTANT
Each blower is statically and dynamically bal
anced as an assembly before installation in the
unit.
ML196DFE units are equipped with a constant torque ECM
motor. It has a DC motor coupled to an electronic control
module both contained in the same motor housing. The mo
tor is programmed to provide constant torque at each of the
five selectable speed taps. Each tap requires 24 volts to en
ergize.
Input Voltage Requirements
The circuit is designed to be operated with AC voltage. To
enable a tap requires 12 to 33VAC. Expected current draw
will be less than 20mA.
Troubleshooting the Motor
Troubleshooting the motor is an easy process. Follow
steps below.
1- Shut off power to unit.
2- Remove input plugs P48 and P49 from motor. See
figure 16 for troubleshooting procedure.
If correct voltage is present in tests 1 and 2 and motor is not
operating properly, replace motor. The motor is not field re
pairable.
If replacing the indoor blower motor or blower wheel is nec
essary, placement is critical. The blower wheel must be cen
tered in the blower housing as shown in figure 13. When re
placing the indoor blower motor the set screw must be
aligned and tightened with the motor shaft as shown in figure
14.
9. Secondary Limit Controls
The secondary limit is located in the blower compartment on
the back side of the blower housing. See figure 15. When ex
cess heat is sensed in the blower compartment, the limit will
open. If the limit is open, the furnace control energizes the sup
ply air blower and closes the gas valve. The limit automatically
resets when unit temperature returns to normal. The secon
dary limit cannot be adjusted.
FIGURE 13
Center Blower Wheel
in Blower Housing
BLOWER WHEEL REPLACEMENT
FIGURE 14
Set Screw
Housing Hub
ALIGN AND TIGHTEN SET SCREW WITH
FLAT SIDE OF MOTOR SHAFT
Motor
Shaft
FIGURE 15
SECONDARY LIMIT CONTROL
Secondary Limits

Page 17
1
2
3
4
5
C
L
G
N
Multi−Meter
(set to VAC)
P48
P49
120 120
Turn on power to unit. Check for 120 volts across terminals
“L” and “N” on input plug P48. If voltage is present continue
to test 2. If voltage is not present problem may be may be up
stream of plug P48 and proceed to test 3.
1
2
3
4
5
C
L
G
N
Multi−Meter
(set to VAC)
P48
P49 24
Switch thermostat to CONTINUOUS FAN MODE. Check for
24 volts across terminal “C” on input plug P48and speed tap
used for continuous fan. (1, 2, 3, 4 or 5) on input plug P49. If
24 volts is not present problem may be up stream of plug P49.
Proceed to test 4.
Multi−Meter
(set to VAC)
120 120
24
Multi−Meter
(set to VAC)
Check for 24 volts across terminals “24 COM” and “FAN” ter
minals on the integrated control. If voltage is present, prob
lem is with the harness. If voltage is not present problem
may be may be with the integrated control
Check for 120 volts across terminals “CIRC” and “Neutrals”
on the integrated control. If voltage is present, problem is
with the harness. If voltage is not present problem may be
may be with the integrated control.
Test 1
Test 2
Test 3 (if necessary)
Test 4 (if necessary)
FIGURE 16

12
3
4
5
6
7
8
9
10
11 12
1/16
TURN
Page 18
Replacing the Motor Module
1. Disconnect electrical power to unit.
2. Remove unit access panel.
3. Unplug the two harnesses from the motor control mod
ule. See figure 17.
TWO HARNESS
CONNECTIONS
MOTOR CONTROL MODULE
MOTOR
FIGURE 17
Unplug the Two Harness Connection
4. Remove the two hex head bolts securing the motor
control module to the motor (see figure 18).
REMOVE BOTH HEX
HEAD BOLTS
FIGURE 18
Remove the Hex Head Bolts
5. Slide the motor control module away from the motor to
access and disconnect the internal three wire connec
tor. It is not necessary to remove blower motor itself.
Set both hex head bolts aside.
Testing the Motor (Figure19)
If any motor fails the below tests, do not install the new con
trol module. The motor is defective and it also must be re
placed. The new control can fail if placed on a defective mo
tor.
1. Using an ohmmeter check the resistance from any one
of the motor connector pins to the aluminum end plate
of the motor. This resistance should be greater than
100k ohms.
2. Check the resistances between each of the three mo
tor connector pins. These should all read approxim
ately the same resistance within an ohm.
3. Check to see if the blower wheel spins freely.
FIGURE 19
Motor Test
TABLE 8
Scale Measurement range in
words ohms
2 M two megohm-two million
ohms 0 - 2,000,000
200 K two hundred kilo-ohm-two
hundred thousand ohms 0 - 200,000
20 K twenty kilo-ohm-twenty
thousand ohms 0 - 20,000
2 K two kilo-ohm two-thousand
ohms 0 - 2,000
200 two hundred ohms 0 - 200
Motor Module Installation
All replacement motor control modules look similar; how
ever, each module is designed for a specific motor size. It is
very important to make sure that you are using the correct
replacement motor control module. USE OF THE WRONG
MOTOR CONTROL MODULE MAY RESULT IN UNEX
PECTED UNIT OPERATION.
1. Verify electrical power to unit is disconnected.
2. Connect three-wire harness from motor to control
module.
3. Mount new motor control module
to motor using two hex head bolts
removed in figure 18. Torque bolts
to 22 inch pounds or 1/16th clock
turn as exampled to the right.
4. Reconnect the two harnesses to
the motor control module.
5. The electrical connectors of the motor should be facing
down to form a drip loop (figure20). This will directs
moisture away from the motor and its electric connec
tions on the motor.
CONNECTOR
ORIENTATION
BETWEEN 4 AND 8
O'CLOCK
BACK OF CONTROL
MODULE
DRIP LOOP
FIGURE 20
Drip Loop

Page 19
II-PLACEMENT AND INSTALLATION
Pipe & Fittings Specifications
All pipe, fittings, primer and solvent cement must conform
with American National Standard Institute and the Ameri
can Society for Testing and Materials (ANSI/ASTM) stan
dards. The solvent shall be free flowing and contain no
lumps, undissolved particles or any foreign matter that ad
versely affects the joint strength or chemical resistance of
the cement. The cement shall show no gelation, stratifica
tion, or separation that cannot be removed by stirring. Re
fer to the table 9 below for approved piping and fitting ma
terials.
CAUTION
Solvent cements for plastic pipe are flammable liq
uids and should be kept away from all sources of
ignition. Do not use excessive amounts of solvent
cement when making joints. Good ventilation should
be maintained to reduce fire hazard and to minimize
breathing of solvent vapors. Avoid contact of ce
ment with skin and eyes.
TABLE 9
PIPING AND FITTINGS SPECIFICATIONS
Schedule 40 PVC (Pipe) D1785
Schedule 40 PVC (Cellular Core Pipe) F891
Schedule 40 PVC (Fittings) D2466
Schedule 40 CPVC (Pipe) F441
Schedule 40 CPVC (Fittings) F438
SDR-21 PVC or SDR-26 PVC (Pipe) D2241
SDR-21 CPVC or SDR-26 CPVC (Pipe) F442
Schedule 40 ABS Cellular Core DWV (Pipe) F628
Schedule 40 ABS (Pipe) D1527
Schedule 40 ABS (Fittings) D2468
ABS-DWV (Drain Waste & Vent)
(Pipe & Fittings) D2661
PVC-DWV (Drain Waste & Vent)
Pipe & Fittings) D2665
PRIMER & SOLVENT CEMENT ASTM
SPECIFICATION
PVC & CPVC Primer F656
PVC Solvent Cement D2564
CPVC Solvent Cement F493
ABS Solvent Cement D2235
PVC/CPVC/ABS All Purpose Cement For
Fittings & Pipe of the same material D2564, D2235, F493
ABS to PVC or CPVC Transition Solvent
Cement D3138
CANADA PIPE & FITTING & SOLVENT
CEMENT MARKING
PVC & CPVC Pipe and Fittings
ULCS636
PVC & CPVC Solvent Cement
ABS to PVC or CPVC Transition Cement
POLYPROPYLENE VENTING SYSTEM ULC-S636
PolyPro
®
by Duravent ULC-S636
InnoFlue
®
by Centrotherm ULC-S636
IMPORTANT
ML196DFE exhaust and intake connections are
made of PVC. Use PVC primer and solvent cement
when using PVC vent pipe. When using ABS vent
pipe, use transitional solvent cement to make con
nections to the PVC fittings in the unit.
Use PVC primer and solvent cement or ABS solvent cement
meeting ASTM specifications, refer to Table 9. As an alter
nate, use all purpose cement, to bond ABS, PVC, or CPVC
pipe when using fittings and pipe made of the same materi
als. Use transition solvent cement when bonding ABS to ei
ther PVC or CPVC.
Low temperature solvent cement is recommended during
cooler weather. Metal or plastic strapping may be used for
vent pipe hangers. Uniformly apply a liberal coat of PVC
primer for PVC or use a clean dry cloth for ABS to clean in
side socket surface of fitting and male end of pipe to depth
of fitting socket.
Canadian Applications Only - Pipe, fittings, primer
and solvent cement used to vent (exhaust) this ap
pliance must be certified to ULC S636 and supplied by a
single manufacturer as part of an approved vent (ex
haust) system. In addition, the first three feet of vent
pipe from the furnace flue collar must be accessible for
inspection.

Page 20
TABLE 10
OUTDOOR TERMINATION USAGE*
Input Size
Vent
Pipe
Dia. in.
STANDARD CONCENTRIC
Flush
Mount
Kit
Wall Kit Wall Ring Kit
Field
Fabricated
1-1/2 inch 2 inch 3 inch
2 inch 3 inch 2 inch
51W11
(US)
51W12
(CA)
22G44 (US)
430G28 (CA)
44J40
(US)
481J20 (CA)
15F74
71M80
(US)
444W92
(CA)
69M29
(US)
444W92
(CA)
60L46 (US)
444W93 (CA)
045
6
1-1/2
3
YES YES
1
YES
1
YES
5
YES
2
YES N/A N/A
2
3
YES YES
1
YES
1
YES
5
YES
2
YES N/A N/A
2-1/2
3
YES YES
1
YES
1
YES
5
YES
2
YES N/A N/A
3
3
YES YES
1
YES
1
YES
5
YES
2
YES N/A N/A
070
6
1-1/2
3
YES YES
1
YES
1
YES
5
YES
2
YES N/A N/A
2
3
YES YES
1
YES
1
YES
5
YES
2
YES N/A N/A
2-1/2
3
YES YES
1
YES
1
YES
5
YES
2
YES N/A N/A
3
3
YES YES
1
YES
1
YES
5
YES
2
YES N/A N/A
090
2
3
YES N/A YES YES
5
YES N/A YES YES
2-1/2
3
YES N/A YES YES
5
YES N/A YES YES
3
3
YES N/A YES YES
5
YES N/A YES YES
110
2
3
YES N/A YES YES
5
YES N/A YES YES
2-1/2
3
YES N/A YES YES
5
YES N/A YES YES
3
3
YES N/A YES YES
5
YES N/A YES YES
NOTE - Standard Terminations do not include any vent pipe or elbows external to the structure. Any vent pipe or elbows external to the structure must be included in total vent length
calculations. See vent length tables.
* Kits must be properly installed according to kit instructions.
1Requires field-provided outdoor 1-1/2” exhaust accelerator.
2Concentric kits 71M80 and 44W92 include 1-1/2” outdoor accelerator, when used with 045 and 070 input models. When using 1-1/2 in. piping, the pipe must be transitioned to 2 in. pipe when
used with the Concentric Kit
3Flush mount kits 51W11 and 51W12 includes 1-1/2 in. outdoor exhaust accelerator, required when used with 045, 070 and 090 input models. When using 1-1/2 in. piping, the pipe must be
transitioned to 2 in. pipe when used with the Flush Mount Kit.
4Termination kits 30G28, 44W92, 4493 and 81J20 are certified to ULC S636 for use in Canada only.
5See table 15 for vent accelerator requirements.
62 inch to 1-1/2 inch reducer required, must be field provided.
Joint Cementing Procedure
All cementing of joints should be done according to the
specifications outlined in ASTM D 2855.
NOTE - A sheet metal screw may be used to secure
the intake pipe to the connector, if desired. Use a drill
or self tapping screw to make a pilot hole.
DANGER
DANGER OF EXPLOSION!
Fumes from PVC glue may ignite during system
check. Allow fumes to dissipate for at least 5 minutes
before placing unit into operation.
1 - Measure and cut vent pipe to desired length.
2 - Debur and chamfer end of pipe, removing any ridges
or rough edges. If end is not chamfered, edge of pipe
may remove cement from fitting socket and result in a
leaking joint.
NOTE - Check the inside of vent pipe thoroughly for
any obstruction that may alter furnace operation.
3 - Clean and dry surfaces to be joined.
4 - Test fit joint and mark depth of fitting on outside of pipe.
5 - Uniformly apply a liberal coat of PVC primer for PVC or
use a clean dry cloth for ABS to clean inside socket
surface of fitting and male end of pipe to depth of fitting
socket.
6 - Promptly apply solvent cement to end of pipe and in
side socket surface of fitting. Cement should be ap
plied lightly but uniformly to inside of socket. Take
care to keep excess cement out of socket. Apply sec
ond coat to end of pipe.
NOTE - Time is critical at this stage. Do not allow prim
er to dry before applying cement.